The present invention relates to an apparatus for electrostatically charging a recording material.
It has been proposed to record deformation images on recording materials having a photoconductive thermoplastic layer by means of the steps of electrostatic charging, imagewise exposure and heating of the layer. Deformation images of this type may be, inter alia, holograms and/or alphanumerical graphic representations.
In a known apparatus for recording deformation images on the recording material, a pliable photoconductive film is, during recording, attracted by electrostatic adhesion to a supporting surface consisting of a glass plate having thereon a conductive transparent layer. A device is provided which separates the recording material from the supporting surface by exerting a pulling action on the recording material at an acute angle to the plane of the surface. After having separated a length of processed material from the supporting surface, which material is transported through the apparatus from a supply reel, the separating device, returns to a position in which it allows build up of the electrostatic charge by guiding the recording material close to the supporting plate. For carrying out the processing steps, for example, electrostatic charging, exposure and thermal development, a control circuit has been proposed which has been modified to control erasure and rerecording steps.
The apparatus charges the recording material by means of a corona discharge device, wherein there is used as the counter-electrode a conductive, transparent layer, supported on a glass plate, over which the recording material is conveyed. The recording material itself does not contain a conductive intermediate layer. In this recording apparatus a relatively large corona voltage, i.e., between 7 and 10 kV is used. The recording material consists of, for example, a 50 .mu.m thick carrier film of polyester having an approximately 2 .mu.m thick photoconductive, thermoplastic layer thereon. The charging is effected over the largest possible surface area from one edge of the recording material to the other so as to ensure optimum use of the recording material for the recordings. In the case of a recording material of 35 mm width, it is desirable to achieve the usual recording width of 24 mm even when recording deformation images. In this case, however, there is the considerable disadvantage that, when charging the marginal areas of the recording material, the corona discharge frequently flashes over the edge of the recording material to the transparent, conductive layer on the glass plate. As a result the transparent, conductive layer may be damped with consequent disturbance of the control process for the series of processing steps.